Chemical vapor deposition (“CVD”) is a gas-reaction process used in the semiconductor industry to form thin layers or films of desired materials on a substrate. High-density-plasma CVD (“HDP-CVD”) processes use a reactive chemical gas along with physical ion generation through the use of an RF generated plasma to enhance the film deposition. In particular, HDP-CVD systems form a plasma that is at least approximately two orders of magnitude greater than the density of a standard, capacitively coupled plasma CVD system by using an inductive coupling technique. In addition, HDP-CVD systems generally operate at lower pressure ranges than low-density plasma systems. The low chamber pressure employed in HDP-CVD systems provides active species having a long mean-free-path and reduced angular distribution. These factors, in combination with the higher plasma density, provide a processing environment that has advantages for certain types of semiconductor processing.
For instance, HDP-CVD techniques have been found to provide improved gapfill capabilities, in which gaps that separate circuit elements and interconnections on substrates are filled with electrically insulative material to prevent the introduction of spurious interactions between the elements. One reason for the improvement in such gapfill capability of HDP-CVD techniques is that they high density of the plasma promotes sputtering simultaneous with film deposition, slowing deposition on certain features, such as the corners of raised surfaces. Some HDP-CVD systems introduce flows of nonreactive gases into the plasma to further promote the sputtering effect and some processes use an electrode within a substrate support pedestal to generate an electric field that biases the plasma towards the substrate.
Recently, a number of processes have been developed that use H2 as a source of the nonreactive gas, with the processes generally using high RF powers to generate the plasma and relatively long depositions times. While these processes have been very successful at filling gaps, they expose portions of the processing chamber to more extended periods of ion bombardment and radiation from high-power plasmas. The effect of this exposure is the absorption of a large amount of heat by ceramic components such as the chamber dome, baffle, gas nozzles, and process kit, particularly during multiple-wafer processes. This high temperature not only results in an increased breakage rate of these components, but may also adversely affect uniformity range drift and increase the incidence of nozzle clogging through the formation of reaction products at these sites.
There is accordingly a general need in the art for improved thermal management of inductively couple plasma reactors.